turquoise (tourquoise) A phosphate CuAl₆(PO₄)₄(OH)₈4–5H₂O; sp. gr. 2.60–2.91; hardness 5.0–6.0; triclinic; sky-blue to blue-green; white or greenish streak; waxy lustre; crystals very rare, normally occurs massive, granular to cryptocrystalline, or as encrusting masses; conchoidal fracture; occurs in veins in association with aluminous, igneous, or sedimentary rocks that have undergone alteration. Finer varieties are used for semi-precious stones.

Turquoise

A number of ancient beliefs surround this stone. J. B. Van Helmont stated: "Whoever wears a Turquoise, so that it, or its gold-setting touches the skin, may fall from any height; and the stone attracts to itself the whole force of the blow, so that it cracks, and the person is safe."

Medieval writers stated that turquoise became paler if its owner was ill, lost color entirely at his or her death, but recovered color when placed upon the finger of a new and healthy owner. It was believed to be a good amulet for preventing accidents to horsemen or becoming tired. Another belief was that turquoise moved itself when any danger threatened its possessor. Turquoise originally came from Persia, where it would sometimes be engraved with a motto or a verse from the Koran. The stone was also prized by Native American healers.

tur·quoise / ˈtərˌk(w)oiz/ • n. 1. a semiprecious stone, typically opaque and of a greenish-blue or sky-blue color, consisting of a hydrated hydroxyl phosphate of copper and aluminum.2. a greenish-blue color like that of this stone: [as adj.] the turquoise waters of the bay.

turquoise precious stone, of sky-blue to applegreen colour. XIV. ME. turkeis, later turkes, turques (XV), turkoise, turquoise (XVI) — OF. turqueise, later -oise, for pierre turqueise ‘Turkish stone’; so called from being first known in Turkestan or conveyed through Turkish dominions.

turquoise Blue mineral, hydrated copper aluminium phosphate, found in aluminium-rich rocks in deserts. Its crystal system is triclinic and it occurs as tiny crystals and dense masses. Its colour ranges from sky-blue and blue-green to a greenish grey and it is a popular gemstone. Hardness 6; r.d. 2.7.